Thoracic Vertebrae (T1-T12)
Vertebrae Thoracicae
location_on Upper and middle back, between the cervical and lumbar spine
The twelve thoracic vertebrae form the middle segment of the vertebral column and are distinguished by their articulation with the ribs via costal facets on the bodies and transverse processes. They increase progressively in size from T1 to T12 and have heart-shaped bodies, long inferiorly-angled spinous processes, and a relatively narrow circular vertebral foramen. The thoracic region is the least mobile spinal segment due to rib cage stabilization.
Key Anatomical Features
- Costal facets (demifacets) on the vertebral bodies articulate with the heads of the ribs
- Transverse costal facets on T1-T10 articulate with the tubercles of the ribs
- Long spinous processes angle sharply downward, overlapping like shingles
- Heart-shaped vertebral bodies increase in size from T1 to T12
- Thoracic kyphosis is the primary curvature present from fetal development
- T11 and T12 are transitional, sharing features with lumbar vertebrae
Muscle Attachments
| Muscle | Attachment | Action |
|---|---|---|
| Erector spinae (iliocostalis thoracis, longissimus thoracis, spinalis thoracis) | Spinous processes, transverse processes, and ribs | Extends and laterally flexes the thoracic spine |
| Multifidus | Transverse to spinous processes spanning 2-4 segments | Stabilizes and extends individual vertebral segments |
| Rotatores thoracis | Transverse to spinous processes | Rotates the thoracic spine (most developed in this region) |
| Semispinalis thoracis | Transverse processes to spinous processes spanning 4-6 segments | Extends and rotates the thoracic spine |
| Trapezius | Spinous processes of T1-T12 | Elevates, retracts, and depresses the scapula |
| Rhomboid major | Spinous processes of T2-T5 | Retracts and elevates the scapula |
Joints and Articulations
| Joint | Type | Connects to |
|---|---|---|
| Costovertebral joints | Synovial plane | Heads of ribs to vertebral body demifacets |
| Costotransverse joints | Synovial plane | Rib tubercles to transverse process facets |
| Thoracic zygapophyseal joints | Synovial plane | Adjacent thoracic vertebrae |
Common Pathologies
Thoracic compression fracture
Wedge-shaped fracture of the vertebral body from axial loading, most common in osteoporotic elderly patients. The thoracolumbar junction (T11-L1) is the most common site.
Scheuermann disease
Developmental condition causing anterior wedging of three or more consecutive thoracic vertebrae, resulting in excessive kyphosis. Typically presents in adolescence.
Thoracic disc herniation
Relatively rare (less than 1% of all disc herniations) but can be dangerous because the thoracic spinal canal is narrow relative to the spinal cord, increasing risk of myelopathy.
Thoracic scoliosis
Lateral curvature of the thoracic spine, most commonly adolescent idiopathic scoliosis. The rib cage rotates with the vertebrae causing a visible rib hump.
Clinical Relevance
The thoracolumbar junction (T11-L2) is the most common site of spinal fractures because it is the transition zone between the rigid thoracic spine (stabilized by the rib cage) and the mobile lumbar spine. Thoracic disc herniations can cause paraplegia due to the narrow spinal canal. The artery of Adamkiewicz, the major blood supply to the lower spinal cord, typically arises from a left intercostal artery between T9 and T12 and must be preserved during thoracic surgery.
Development and Ossification
Each thoracic vertebra ossifies from three primary centers (one body, two neural arches) appearing during weeks 8-10 of fetal development. Additional secondary centers appear at puberty for the ring apophyses (superior and inferior surfaces of the body), spinous process tip, and transverse process tips. These fuse by age 25.
Did You Know?
- The thoracic spine is the only region where vertebrae articulate with ribs
- The natural thoracic kyphosis is present before birth and is called a primary curvature
- Thoracic vertebrae spinous processes overlap so much that a knife wound between them would need to angle upward to enter the spinal canal
Frequently Asked Questions
How many thoracic vertebrae are there?
There are 12 thoracic vertebrae, labeled T1 through T12. They make up the middle segment of the vertebral column, between the cervical and lumbar regions.
What is unique about thoracic vertebrae?
Thoracic vertebrae are the only vertebrae that articulate with the ribs. Each thoracic vertebra has costal facets on its body and transverse processes for rib attachment. They also have longer, downward-pointing spinous processes compared to cervical vertebrae.
Where is T12 located in the spine?
T12 is the lowest thoracic vertebra, located at the junction between the thoracic and lumbar spine. It sits roughly at the level of the lowest rib and marks the transition point where the spine begins to curve forward into the lumbar lordosis.
What is the function of thoracic vertebrae?
The thoracic vertebrae protect the spinal cord, support the rib cage, and allow limited rotation of the trunk. They bear increasing body weight from T1 to T12 and provide attachment points for the ribs, back muscles, and ligaments.
What are atypical thoracic vertebrae?
T1, T10, T11, and T12 are considered atypical thoracic vertebrae. T1 has a complete costal facet and resembles a cervical vertebra. T10 has only one costal facet. T11 and T12 have no facets on their transverse processes and resemble lumbar vertebrae.
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